1. Field of the Invention
The present invention relates to a production method of a fluid dynamic bearing, a fluid dynamic bearing, a spindle motor, and a disk driving apparatus.
2. Description of the Related Art
A hard disk drive or an optical disk drive is provided with a spindle motor to rotate a disk around a center axis thereof. The spindle motor relatively rotates a stationary portion and a rotating portion via a bearing. In recent years, a fluid dynamic bearing is often used as a bearing for the spindle motor. In the fluid dynamic bearing, lubricating fluid is interposed between a shaft and a sleeve, so as to relatively rotate the shaft and the sleeve by means of dynamic pressure in the lubricating fluid.
The construction of such a fluid dynamic bearing is described in Japanese Laid-Open Patent Publication No. 2003-88042, for example.
In a conventional fluid dynamic bearing, an annular rotor hub extending in a radial direction is fixed to an upper portion of a shaft. On the other hand, a bottom surface of a rotor hub is opposed to a top surface of the sleeve via the lubricating fluid. In order to increase the sliding property between the rotor hub and the sleeve, or in order to suppress the damage due to the contact between the rotor hub and the sleeve, a film with high lubricating property is sometimes formed on the bottom surface of the rotor hub, or the like.
The film is generally formed in such a manner that a liquid for forming the film is applied and spread, and then the solvent is dehydrated. However, if the film is formed beyond the range to be coated with the film, the film may disadvantageously be in contact with another member on the outside of the desired range. This possibly causes the rotational characteristics of the motor to significantly deteriorate, or causes device defect to occur. For this reason, a technique for forming the film only in a required range is desired.